1. Field of the Invention
The present invention relates to a transmission controlling method preferably applicable to a case where, for example, various kinds of information are transmitted over a radio signal, thereby constructing a local area network (LAN) among plural equipments, a transmission control apparatus to which this controlling method is applied and a transmitting apparatus whose transmission is controlled by this transmission control apparatus.
2. Description of the Related Art
In the past, when constructing a local area network within a comparatively narrow area such as a household and an office or the like, so that, between plural equipments such as various kinds of video equipments, a personal computer system and its peripheral devices or the like, data handled by these equipments can be transmitted, it may be arranged that, instead of directly connecting between the respective equipments through some signal lines, a transmitting/receiving apparatus of the radio signal (radio transmitting apparatus) is connected to each equipment, thus allowing the data to be transmitted by radio transmission.
Constructing the local area network by radio transmission eliminates the necessity to directly connect the respective equipments by signal lines, etc., which enables the system structure to be simple.
Incidentally, when a plurality of the radio transmitting apparatus are prepared to construct the local area network, if signals are simultaneously transmitted from the plurality of transmitting apparatus by using the same transmission band, a transmission error may occur. For this reason, it is necessary to control the access in communication between the respective transmitting apparatus within the network by some means.
As concerns an access controlling method known from the past, for example, in case of a small-scale radio network, there is a method in which a central transmitting apparatus (root node) in the star connection is made a control station and the control station manages in a unified manner the communication among the respective transmitting apparatus (node) within the network.
Incidentally, the radio network system having such a control station determined involves a problem in which, when a need of renewing management information transmitted from the control station arises, it is complicated to process for transmitting securely the management information to each terminal station.
Specifically, for example, in a conventional system, in order to confirm that renewal information of the management information from the control station has reached each terminal station, each terminal station is caused to reply with confirming information (ACK signal) for confirming completion of connection. In other words, when renewing the network management information, the control station transmits simultaneously the renewal information to all the terminal stations by broadcast transmission and thereafter each terminal station is caused to return the confirming information when it has received correctly the renewal information. The returned confirming information is judged by the control station. These processings involve a problem in which transmission traffic for processing to transmit the control information becomes redundant. Particularly, there is a fear that an enormous time is consumed to return the confirming information over a radio transmission path whose quality is poor.
If it takes time to transmit this control information, for example, in case of a communication structure having a management information transmitting area for the network management and an information transmitting area for transmitting real information, when the renewal information is to be transmitted by using this information transmitting area, it will take a long time until an information transmission using the information transmitting area is started by the renewed control information.
Therefore, in recent years, usefulness of the transmission controlling method is being recognized, in which a so-called connectionless protocol that prior to the information transmission no establishment of transmission path takes place is used on the radio transmission path. However, in the case of the transmission controlling method using the connectionless protocol, because any information is broadcast on the radio transmission path while no assurance of connection is obtained, there is a danger that transmissions from the plural stations collide one another to cause the transmission error.
When the control station instructs, using the management information transmitting area, to renew information on a utilizing method of the transmission path on the information transmitting area, communicating stations which fail to receive that management information cannot renew the utilizing method of transmission path on the information transmitting area.
Moreover, when a communication network configuration is considered, in which each terminal station has a plurality of directive antennas and an equipment making an antenna diversity operation to switch the antenna used for transmission or reception depending on a communicating partner, it cannot be assured that an optimum antenna is selected at a timing when the network management information is transmitted, thus causing a need to define the strict timing. Furthermore, for an always moving station, the optimum antenna will change whenever it moves and so the renewal of information with a specific timing becomes complicated.
Also, when any transmission controlling method may be employed, it needs some time to decode those transmission management information and thus it is very difficult to renew the transmission management information in an instant. Particularly, in transmission subjected to digital modulation/demodulation, the error correction is often performed in order to improve the line quality of transmission path and so it takes a time to decode these information also. This makes it difficult for each terminal station to renew simultaneously the management information.
An object of the present invention is to make it possible to renew the transmission control information satisfactorily under simple processing when performing the transmission control within the network by providing the control station.
A transmission controlling method according to the present invention is arranged so that, when the control information to be set by the control station is to be renewed, the control station may transmit the control information to be renewed as well as its renewed timing information prior to the renewed timing and the communicating stations renew the control information to the received control information with the timing set by received timing information.
According to this transmission controlling method, in each communicating station, the previously transmitted renewal information is set and then the control information is renewed simultaneously by the set renewal information with the specified timing.
A transmission control apparatus according to the present invention comprises a renewal information producing means for producing the renewal information of the control information which controls access within the network, a timing specifying means for giving timing information which specifies a timing for renewing with the renewal information produced by the renewal information producing means, and a transmitting means for transmitting the renewal information produced by the renewal information producing means as well as the timing information given by the time specifying means.
According to this transmission control apparatus, when controlling other transmitting apparatus within the network to renew the control information, it is enabled to specify the timing of renewing the control information.
A transmitting apparatus according to the present invention comprises a communicating means for transmitting and receiving to and from other transmission apparatus as well as for receiving the control information from a control apparatus, and a control means for estimating the control information received by the communicating means to cause the communicating means to transmit or receive and when the received control information contains renew information and timing information, renew the control information to the renewal information at a timing specified by the timing information.
According to the transmitting apparatus, it is possible to renew the control information by the received renewal information at a timing specified from the control apparatus.